Disturbing footage has been released capturing the moment a diver begins to drown 100 feet below the surface in Texas' deadliest cave.

The 'free-diver' is seen swimming towards the beacon of light as he tries to escape the enclosing underwater labyrinth.

He loses his flipper in the ordeal and has to abandon his weight-belt in order to make it out alive. He can be heard gasping for air as he swims around the cave relying only on the capacity of his lungs.

The diver can be seen reaching towards the light

The gargling noise is a natural occurrence called the mammalian dive reflex which prevents lungs from collapsing during long spells underwater.

The unnamed diver can be seen emerging from the endless pit at the end of the video.

The cave, named Jacob's Well, fools some underwater explorers with its intricate tunnels. One source claims that there's a 'chimney' in the chamber which disguises itself as an exit out of the underwater pit.

Jacob's Well is a popular spot for thrill seekers and tourists

According to the Associated Press, at least nine people have lost their lives from either attempting some kind of daredevil stunt into the seemingly endless abyss or diving below the surface and exploring the well’s cave system.

Located about an hour outside of Austin, Texas, it's reported to have first been discovered in the 1850s and in it's early years it was a gathering place for Native American tribes.